An Early Alert for Landslides

Geologist Mark Bulmer of the University of Maryland Baltimore County and his colleagues have figured out a way to predict when unstable slopes will suddenly give way to deadly landslides. The scientists have identified two characteristic patterns of surface motion preceding the event: Either the ground deforms gradually like Silly Putty, or it cracks abruptly when the underlying rock gives way. "You can look at a plot and make a pretty good forecastaccurate to within a few daysof when the landslide is going to move catastrophically," Bulmer says. Analyzing ground-deformation data from eight past landslides, he finds he could have predicted all of them within a few days of when they actually broke loose.

Bulmer's team is using this technique to monitor landslides at high-risk locations in California, England, Italy, and Taiwan. Ground-based measurements can fill in only part of the picture, so the researchers are combining them with radar data from the ERS-1, ERS-2, and Radarsat satellites, which can identify shifts in the earth as small as a few tenths of an inch. Global, real-time landslide forecaststhe kind that could forecast common and often lethal rainfall-triggered events would require a dedicated, high-resolution satellite. But Bulmer says current resources are good enough to anticipate catastrophes such as the 1963 Vaiont landslide in northern Italy, which took more than 2,000 lives.